WebAssembly functions often have subsequent memory accesses, and each of
these memory accesses need the start address of the memory in a register.
With this CL the register with the memory start address is cached, so
only the first memory access has to load the memory start address into a
register, subsequent memory accesses can just reuse the register.

In first measurements with the epic benchmark this reduces the size of
the generated Liftoff code by a bit more than 5%.

R=clemensb@chromium.org

Bug: v8:11862
Change-Id: Ic33e7e3c00a4209570821269c728187affbeadcf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2947403
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75113}